This invention relates to devices for collecting solar energy on members exposed to the sun's rays and transferring the heat collected thereby to a circulating fluid for utilization in any desired manner. The most well known of these devices are called flat plate collectors since the members exposed to the sun are simple flat plates. Another collector device, disclosed in my copending application entitled Solar Energy Collector Device filed Jan. 21, 1977, Ser. No. 761,422, uses extended tubes having openings therein as the solar energy collection members. Specifically, the present invention relates to an improvement in these devices wherein the heat flow through the collector device itself is enhansed.